This invention relates to window frames and particularly to window frames manufactured from a plurality of frame parts, each of which is cut from a pultruded profile of a glass fibre reinforced resin material.
In recent years there have been many different materials used to replace the original conventional wooden window frames. These materials need to be sufficiently rigid to support the window pane, resistant to corrosion or other deterioration from exposure to the various aspects of the weather, capable of supporting weatherstripping and firmly engaging an adjacent surface to provide seals against the transmission of air and preferably of a low thermal conductivity in order to avoid the transmission of heat from the inside of a building to the outside of a building. Various materials have been used particularly aluminum and vinyl.
It is also important that the material can be formed in an extrusion-type process so that long lengths of a constant cross section can be formed for cutting into desired lengths for assembly into a generally rectangular window frame.
The materials presently on the market have various disadvantages which are well known in the trade and need not be discussed at length here. At various times in past years attempts have been made or consideration has been given to manufacture of window frames of this type from glass fibre reinforced resin material. However, these attempts and considerations have met with serious problems which have prevented the product being commercially marketed.
One problem which has arisen with pultrusions is that of manufacturing a suitable corner for coupling the frame parts together at the corners to form generally a rectangular window frame. Techniques previously used for aluminum, vinyl and wood are unsatisfactory in view of the different structure and strength characteristics necessary for forming the window frame profile by pultrusion.